The present invention relates to an aluminum material for brazing, a method of manufacturing the same, and a method of manufacturing a heat exchanger of aluminum alloy which may be used as a condenser for an air conditioner of an automobile.
Conventional aluminum brazing material for use in a heat exchanger of the above-described type and a method of manufacturing the same are disclosed in Japanese Patent Laid-Open Publications Nos. 58-204169 and 59-10467.
In the former Publication, zinc is spray-coated on the surface of an extruded tube of aluminum alloy, and both this tube and corrugated fins- with a brazing material coated thereon are brazed in a furnace so as to produce a heat exchanger.
In the latter Publication, a brazing alloy of aluminum and silicon is sprayed on the surface of an extruded tube of aluminum alloy so as to produce the tube for a heat exchanger.
However, these techniques disclosed in the
Japanese Patent Laid-Open Publications Nos. 58-204169 and 59-10467 suffer from the following problems: in a case where the brazing alloy of Al and Si is coated on an extruded multi-hole tube, a resultant aluminum alloy heat exchanger produced therefrom has poor corrosion resistance, even though excellent brazing is possible between the multi-hole tube and the corrugated fins. In contrast, in another case of coating Zn on such a multi-hole tube, a resultant heat exchanger produced therefrom has excellent corrosion resistance, but if fluoride type flux is used for the brazing, the zinc layer melts before the melting of the flux, so that it becomes impossible for the flux to reach the whole of the surfaces which are to be brazed, with the result that inferior brazing is apt to occur.
On the other hand, in a case where there is used a method of coating on an extruded tube an alloy of Al, Si and Zn which alloy contains a large amount of Zn, the whole of the alloy of Al, Si, and Zn melts at one melting point during the heating thereof for brazing before the Zn diffuses on the tube, so that the melted alloy is gathered in the vicinity of the contact portions of the tube and the fin with the result that the Zn contained in the alloy can not be well diffused over the whole of the tube.